From 9df51b51b8d0724159e64c28a294d217de036184 Mon Sep 17 00:00:00 2001
From: Kae <80987908+Novaenia@users.noreply.github.com>
Date: Thu, 12 Sep 2024 23:06:13 +1000
Subject: [PATCH] fix windows pread and pwrite bug

reading without a byte offset specified can affect absolute reads afterward, this is a workaround (thanks windows...)
---
 source/core/StarFile_windows.cpp | 14 +++++++-------
 source/core/StarImage.cpp        |  7 +++----
 2 files changed, 10 insertions(+), 11 deletions(-)

diff --git a/source/core/StarFile_windows.cpp b/source/core/StarFile_windows.cpp
index 0b5c286..6352bb7 100644
--- a/source/core/StarFile_windows.cpp
+++ b/source/core/StarFile_windows.cpp
@@ -18,13 +18,11 @@
 
 namespace Star {
 
-namespace {
-  OVERLAPPED makeOverlapped(StreamOffset offset) {
-    OVERLAPPED overlapped = {};
-    overlapped.Offset = offset;
-    overlapped.OffsetHigh = offset >> 32;
-    return overlapped;
-  }
+OVERLAPPED makeOverlapped(StreamOffset offset) {
+  OVERLAPPED overlapped = {};
+  overlapped.Offset = offset;
+  overlapped.OffsetHigh = offset >> 32;
+  return overlapped;
 }
 
 String File::convertDirSeparators(String const& path) {
@@ -378,6 +376,7 @@ size_t File::pread(void* f, char* data, size_t len, StreamOffset position) {
   DWORD numRead = 0;
   OVERLAPPED overlapped = makeOverlapped(position);
   int ret = ReadFile(file, data, len, &numRead, &overlapped);
+  fseek(f, -(StreamOffset)numRead, IOSeek::Relative);
   if (ret == 0) {
     auto err = GetLastError();
     if (err != ERROR_IO_PENDING)
@@ -392,6 +391,7 @@ size_t File::pwrite(void* f, char const* data, size_t len, StreamOffset position
   DWORD numWritten = 0;
   OVERLAPPED overlapped = makeOverlapped(position);
   int ret = WriteFile(file, data, len, &numWritten, &overlapped);
+  fseek(f, -(StreamOffset)numWritten, IOSeek::Relative);
   if (ret == 0) {
     auto err = GetLastError();
     if (err != ERROR_IO_PENDING)
diff --git a/source/core/StarImage.cpp b/source/core/StarImage.cpp
index 52c2370..c7d4962 100644
--- a/source/core/StarImage.cpp
+++ b/source/core/StarImage.cpp
@@ -18,13 +18,12 @@ void readPngData(png_structp pngPtr, png_bytep data, png_size_t length) {
 };
 
 bool Image::isPng(IODevicePtr device) {
-  png_byte header[8];
-  device->readAbsolute(0, (char*)header, sizeof(header));
-  return !png_sig_cmp(header, 0, sizeof(header));
+  png_byte header[8]{};
+  return !png_sig_cmp(header, 0, device->readAbsolute(0, (char*)header, sizeof(header)));
 }
 
 Image Image::readPng(IODevicePtr device) {
-  png_byte header[8];
+  png_byte header[8]{};
   device->readFull((char*)header, sizeof(header));
 
   if (png_sig_cmp(header, 0, sizeof(header)))